Antarctica : what temperature variations since the last ice age ?

CNRS press release

Antarctica has experienced substantial temperature changes, particularly since the last ice age. An international collaboration involving CNRS scientists [1] has just challenged previously accepted estimates of these variations with new measurements published June 4, 2021 in Science. Their study highlights the differences between the functioning of East and West Antarctica, linked in particular to different variations in their altitude.

– Scientists have produced the most reliable estimates to date of past temperature variations in Antarctica.
– They point out notable differences between the functioning of West and East Antarctica.
– This study allows us to test and consolidate future climate projections.

Antarctic surface temperatures have increased significantly since the last ice age. Understanding this evolution is crucial in order to study climate change at all times and to test our ability to model it. A study involving French scientists provides the most reliable estimates to date of past temperature variations in Antarctica. While the warming since the Ice Age was estimated at +9°C over the whole continent, the new measurements reveal a variation of +10°C in West Antarctica and between +4 and +7°C in East Antarctica.

Until now, scientists have been estimating ancient temperatures using an isotopic thermometer, i.e. by analyzing the proportion of isotopic forms of water. However, the accuracy of this method relies on a calibration difficult to implement in Antarctica. Two new independent methods have been implemented to overcome this problem. The first is to measure the temperature in the boreholes obtained after coring
The French teams have provided and interpreted temperature measurements from the Epica borehole at Concordia and analyses of the past atmosphere from the ice cores. The measurements provided in the Epica borehole were made possible by recurrent funding from the French Polar Institute IPEV]]. The great thickness of the ice layers in Antarctica makes it possible to keep track of and reconstruct past temperatures. The second method is based on the process of snow densification, which is sensitive to temperature and can be detected by analyzing the atmosphere trapped in the ice cores. These two measurements have given similar results, confirming their reliability.

This work highlights the role played in Antarctica by variations in ice altitude on temperature changes. They reflect the marked differences between East Antarctica, which has increased slightly in altitude since the Ice Age, and West Antarctica, which has decreased considerably. These data were confronted with climate models [2], in order to refine the understanding of past temperature changes and to have better confidence in future projections.

Reference
C. Buizert, T. J. Fudge, W. H. G. Roberts, E. J. Steig, S. Sherriff-Tadano, C. Ritz, E. Lefebvre, J. Edwards, K. Kawamura, I. Oyabu, H. Motoyama, E. C. Kahle, T. R. Jones, A. Abe-Ouchi, T. Obase, C. Martin, H. Corr, J. P. Severinghaus, R. Beaudette, J. A. Epifanio, E. J. Brook, K. Martin, J. Chappellaz, S. Aoki, T. Nakazawa, T. A. Sowers, R. B. Alley, J. Ahn, M. Sigl, M. Severi, N. W. Dunbar, A. Svensson, J. Fegyveresi, C. He, Z. Liu, J. Zhu, B. Otto-Bliesner, V. Y. Lipenkov, M. Kageyama, and J. Schwander : Antarctic surface temperature and elevation during the Last Glacial Maximum., Science, 4 June 2021. DOI.

► Also read the communiqué published by the CNRS.

Translated with www.DeepL.com/Translator (free version)

Slider image : Sarah Del Ben Wiltouch Fondation UGA